Restarting arrangement for high-pressure mercury-vapor lamp which includes metallic halide additives

ABSTRACT

High-pressure mercury-vapor discharge lamp which includes metallic halide additives is adapted to be operated in a horizontal orientation. To restart the lamp when it is still hot from being operated, an elongated electrically conductive refractory member is positioned proximate the outer surface of the arc tube and extending longitudinally thereof. The conductive member is electrically insulated from the lamp electrodes and is positioned generally diametrically opposite the lowest longitudinally disposed portion of the arc tube where the metallic halide has condensed.

United States Patent Inventors Appl. No.

Filed Patented Assignee Priority Horst Grabner; Herbert Konow, both ofMunich, Germany Aug. 14, 1969 Oct. 5, 1971 Patent-Trevhand-GesellschaitFur Elektrische Gluklampen m.b.I-I. Munich, Germany Aug. 21, 1968Germany RESTARTING ARRANGEMENT FOR HIGH- PRESSURE MERCURY-VAPOR LAMPWHICH INCLUDES METALLIC I-IALIDE ADDITIVES 7 Claims, 1 Drawing Fig.

US. Cl 313/25, 313/184, 313/201 Int. Cl ..H0lj 61/12, I-IOlj6l/34,1-I0lj 61/54 Field of Search 313/184, 201, 25, 197

WlRE STARTING A|D 3 9 METALLIC HALIDE CONDENSATE/ 2 Ileferences UNITEDSTATES PATENTS 1,961,618 6/1934 Machlett 313/197 2,056,613 10/1936Mitchell 313/197 2,094,647 10/1937 Freitag et a1 313/197 2,491,85412/1949 Force 313/201 X 2,252,638 8/1941 McCauley 313/201 X 2,542,3452/1951 Miles 313/201 2,841,733 7/1958 Hodge... 313/184 3,431,447 3/1969Larson 313/25 Primary Examiner-Roy Lake Assistant Examiner-Palmer C.Demeo Attorneys-A. T. Stratton and W. D. Palmer ABSTRACT: High-pressuremercury-vapor discharge lamp which includes metallic halide additives isadapted to be operated in a horizontal orientation. To restart the lampwhen it is still hot from being operated, an elongated electricallyconductive refractory member is positioned proximate the outer surfaceof the arc tube and extending longitudinally thereof. The conductivemember is electrically insulated from the lamp electrodes and ispositioned generally diametrically opposite the lowest longitudinallydisposed portion of the arc tube where the metallic halide hascondensed.

PATENTED om 5l97l IIIITI1 RESTARTING ARRANGEMENT FOR HIGH-PRESSUREMERCURY-VAPOR LAMP WHICH INCLUDES METALLIC HALIDE ADDITIVES BACKGROUNDOF THE INVENTION The invention relates to an arrangement for restartinga high-pressure mercury-vapor electric discharge lamp with additives ofmetal halogen compounds when the lamp is still hot from operation, saidlamp enclosed in an outer envelope and connected with an ignitiondevice. The electrode spacing is a multiple of the envelope diameter.

High-pressure mercury-vapor electric discharge lamps, more particularlylamps with metal halide additives, are of high efficiency and, for thisreason, are used for general lighting services such as, for example,lighting of streets or athletic grounds. It is well known that all thehigh-pressure mercury-vapor electric discharge lamps, once they havebeen switched off, cannot immediately be started again without startingaid due to the high operating pressure, and this proves unsatisfactory,even for restarting after temporary interruptions of the power supply.For hot start by means of highfrequency pulses, high voltages arerequired exceeding 50kv. and pulse sequences of at least per half cycleeach. In addition, it is well known to use in such lamps metal halideadditives, saturated halide vapors, or excess of halogen in order toobtain optimum efficiency and high color rendition. This leads to asevere handicap for hot start, for in this case the requisite startingvoltages and pulse sequences are considerably higher. In horizontaloperating position, a conductive condensate of the metal halogen ispresent in most cases at the bottom of the arc tube. Even with extremestarting efforts it is impossible in this case to start the lamp. Thespark flashes over from the electrodes to the condensate across theshortest distance, and the discharge path is not ionized.

SUMMARY OF THE INVENTION The foregoing problem is solved according tothe invention by the arrangement for restarting a high-pressuremercuryvapor electric discharge lamp with additives of halogen compoundswhen the lamp is still hot from operation, said lamp being enclosed inan outer envelope and connected with an ignition device wherein theelectrode spacing is larger than the bulb diameter, said arrangementcharacterized in that a starting aid with open potential is provided onthe outer wall surface of the discharge tube and parallel to its longaxis on the side opposite to the condensate of the metal halides.

BRIEF DESCRIPTION OF THE DRAWING In the sole FIGURE of the drawing isillustrated an elevational view of a highpressure mercury-vapordischarge device which includes a metallic halide additive, and whichlamp is provided with a metallic starting aid in accordance with thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT When the starting aid is used,the spark most surprisingly does not flash over to the condensate butpasses from the electrode along the upper portion of the discharge tube,parallel to the starting aid, to the opposite electrode. By this means aconductive channel of ionized gas is established and the lamp can bestarted. Pursuant to the invention it is necessary that the conductivityof the starting aid is at least one magnitude higher than that of thecondensate. The specific resistance of the starting aid should besimilar to the resistance of metals, preferably below 3Qmm./m. Inaccordance with the invention, a wire not too small in thickness is usedwhich is inserted in a narrow quartz capillary and is of refractorymetal because of the high bulb wall temperature; moreover, the wireshould have as low a coefficient of expansion as possible. For example,a refractory wire of 0.6 mm. in diameter of an ironchromium-aluminumalloy has proved suitable. A starting strip such as is used, forexample, with photoflash lamps, cannot be used in lamps according to theinvention due to its high resistance to conduction and the high bulbtemperature of from 800 to 900 C. The present starting aid, incontradistinction to conventional forms of construction of HPM electricdischarge lamps, is without fixed potential, i.e. it is neither directlynor indirectly electrically conductively connected with any part of thelamp but acts capacitively. The ignition wire extends along the wall ofthe discharge tube from electrode to electrode and is directly affixedto the discharge tube. For this purpose, for example, loops of quartzglass are provided on the discharge tube through which the ignition wireis passed and bent off at its ends. Altemately, a plurality of ignitionwires distributed over the circumference of the discharge tube may beused as starting aid.

The arrangement of the starting aid according to the invention alsopermits, in case of mercury-metal halide lamps, the use of ignitiondevices of conventional size, even in case of high lamp wattages. Due tothe high voltages applied to the lamp, the lead-in wires are passed outof the outer envelope at a respective distance from one another.Generally, they are passed out at opposite ends of the outer envelope.

The outer envelope may be evacuated, mainly in case of lamps rated forlower wattages. On account of improved heat dissipation it is, however,advantageous if the outer envelope of high wattage lamps is filled withan inert gas such as, for example, nitrogen. In this case, care has tobe taken that the atmosphere in the outer envelope is not more readilyionizable than the atmosphere in the discharge tube in order to avoid ashort circuit by an unintended discharge in the outer envelope.Accordingly, a pressure exceeding 300 tons is chosen, preferably 600torrs.

The invention will now be described by way of example in theaccompanying drawing:

The high pressure electric discharge lamp comprises the discharge tube 1of quartz glass, the electrodes 2 and 3, and one lead-in wire 4 and 5all enclosed in an outer envelope 6 provided with bases 7 and 8. Thediameter of the discharge tube 1 is 45 mm., the electrodes 2 and 3 arespaced apart a distance of 220 mm. The lamp discharge tube is filledwith l mg./cc. of mercury, 2 mgrs/cc. of sodium iodide, 0.4 mg./cc. ofthallium iodide, and with a basic argon gas at a pressure of 50 torrs.The condensate 9 of metal halide is also present on the wall of the arctube during operation of the lamp. The lamp is operated at 18 amperesand 250 volts and a wattage of 4 kw. Starting of the cold lamp andrestart are effected by means of a conventional ignition device, notshown, to which the electrodes 2 and 3 are adapted to be electricallyconnected. The quick restart is rendered possible by starting aid 10which comprises, for example, a refractory wire 12 of an alloycomprising about 65 percent by weight iron, 30 percent by weightchromium and 5 percent by weight aluminum. The wire 12 is 0.6 mm. indiameter and 220 mm. in length, and is enclosed in a capillary ll ofquartz, and the wire conductivity amounts to about times the maximumconductivity of the condensate. The wire 12 is held on the dischargetube 1 by the loops I3 and 14 of quartz glass. The outer envelope 6 ofthe embodiment is filled with nitrogen at a pressure of 600 torrs. Thediameter of the outer envelope 6 is about three times the diameter ofthe discharge tube.

With the starting-aid arrangement of the invention, restart of the lampoccurs after the extremely short interval of about 1 second, withoutrequiring a more complex ignition device.

We claim:

1. In combination with a high-pressure mercury-vapor discharge lampwhich is adapted to be operated in a generally horizontal orientationand which comprises an elongated light-transmitting arc bulb adapted tobe disposed generally horizontally during operation and havingelectrodes operatively disposed therein proximate the ends thereof, thespacing between said electrodes being greater than the diameter of saidarc-enclosing bulb, said electrodes adapted to be electrically connectedto an external source of starting and energizing potential, adischarge-sustaining filling within said arc-enclosing bulb andcomprising mercury and metallic halide, said metallic halide condensedproximate the lowest longitudinal portion of said arc-enclosing bulb,and an outer bulb surrounding said arc-enclosing bulb, the improvedstructure for starting said lamp when it is still hot from operation,which structure comprises: an elongated electrically conductiverefractory member having an electrical conductivity substantiallygreater than that of said condensed metallic halide and positionedexteriorly of and proximate the outer surface of said arc-enclosing bulband extending longitudinally thereof, said member also positionedgenerally diametrically opposite the lowest longitudinally disposedportion of said arc-enclosing bulb, and said member insulated fromdirect electrical connection with said electrodes.

2. The combination as specified in claim I, wherein said conductiverefractory member has an electrical conductivity which is at least timeshigher than the conductivity of said condensed metallic halide.

3. The combination as specified in claim 1, wherein the specificresistance of said conductivity refractory member is less than 3 ohm mm4 The combination as specified in claim 2, wherein said conductiverefractory member is formed as a wire and extends longitudinally alongsaid arc-enclosing bulb from one of said electrodes to the other of saidelectrodes, and said wire is substantially enclosed throughout itslongitudinal dimension by a quartz capillary member.

5. The combination as specified in claim 4, wherein said wire is affixedto the exterior surface of said arc-enclosing bulb by means of quartzformed as loops.

6. The combination as specified in claim 1, wherein said outer bulb isevacuated.

7. The combination as specified in claim 1, wherein said outer envelopeis filled with inert gas at a pressure exceeding 300 torrs.

1. In combination with a high-pressure mercury-vapor discharge lampwhich is adapted to be operated in a generally horizontal orientationand which comprises an elongated light-transmitting arc bulb adapted tobe disposed generally horizontally during operation and havingelectrodes operatively disposed therein proximate the ends thereof, thespacing between said electrodes being greater than the diameter of saidarc-enclosing bulb, said electrodes adapted to be electrically connectedto an external source of starting and energizing potential, adischargesustaining filling within said arc-enclosing bulb andcomprising mercury and metallic halide, said metallic halide condensedproximate the lowest longitudinal portion of said arc-enclosing bulb,and an outer bulb surrounding said arc-enclosing bulb, the improvedstructure for starting said lamp when it is still hot from operation,which structure comprises: an elongated electrically conductiverefractory member having an electrical conductivity substantiallygreater than that of said condensed metallic halide and positionedexteriorly of and proximate the outer surface of said arc-enclosing bulband extending longitudinally thereof, said member also positionedgenerally diametrically opposite the lowest longitudinally disposedportion of said arc-enclosing bulb, and said member insulated fromdirect electrical connection with said electrodes.
 2. The combination asspecified in claim 1, wherein said conductive refractory member has anelectrical conductivity which is at least 10 times higher than theconductivity of said condensed metallic halide.
 3. The combination asspecified in claim 1, wherein the specific resistance of saidconductivity refractory member is less than 3 ohm mm.2.
 4. Thecombination as specified in claim 2, wherein said conductive refractorymember is formed as a wire and extends longitudinally along saidarc-enclosing bulb from one of said electrodes to the other of saidelectrodes, and said wire is substantially enclosed throughout itslongitudinal dimension by a quartz capillary member.
 5. The combinationas specified in claim 4, wherein said wire is affixed to the exteriorsurface of said arc-enclosing bulb by means of quartz formed as loops.6. The combination as specified in claim 1, wherein said outer bulb isevacuated.
 7. The combination as specified in claim 1, wherein saidouter envelope is filled with inert gas at a pressure exceeding 300torrs.